We've been using Combat Companion ever since it came out and the players just love it. It has improved the flavor of combat for non, semi and even pure spell users. In a campaign that we finished last year most where martial artists and it did not change that feeling. One of the players even built for herself a monk with archery as focus, and the rules in the Combat Companion never faltered. Priests can create defensive styles to last longer, Magicians can combine bolts to make development easier, fighters can stack some 2 or 3 great styles with multiple attacks, etc.
Also, our rule set is mainly RMFRP, and we've had no big problems adapting the small differences. The book is full of suggestions on how to be applied to RMFRP.